Over the past few decades, vibration mitigation research has largely transitioned from traditional active control techniques and pursuit of materials with stronger damping properties to the notion of artificially engineered structures which possess a set of unique wave attenuation features that are otherwise elusive [1]}, [2]}. Most notable among these are Phononic Crystals (PnCs), a class of periodic structures which come in continuous (e.g., rods [3]}, beams [4]}, and plates [5]}) or discrete (e.g., spring-mass chains [6]} and lattices [7]}) forms. PnCs exhibit bandgaps, i.e., frequency regions of forbidden wave propagation, which arise from destructive interferences at interfaces with impedance mismatches. These mismatches are most commonly created by layering two or more materials in a spatially periodic manner with the smallest self-repeating block being referred to as the PnC's unit cell. Owing to their ability to manipulate incident vibroacoustic excitations, PnCs have been extensively used in a broad range of applications ranging from energy harvesting [8]}, [9]} and attenuation of airborne sound [10]}, to nonreciprocal wave transmission [11]}, [12]} and ultrasonic wave focusing [13]}.
